I. Field of Invention
The present invention concerns a microfluidic device in which there is a microchannel structure which comprises (a) one or more inlet ports, (b) one or more outlet ports, and (c) a structural unit which comprises a fluidic function and is located between one of the inlet ports and one of the outlet ports. The structural unit (c) may include an inlet or an outlet port.
According to the invention the structural unit is selected by certain innovative structures permitting a) retaining nl-aliquots of liquids in which the constituents have been defined by mixing of aliquots within the microfluidic device (unit A), b) mixing of aliquots of liquids (unit B), c) partition of larger aliquots of liquids into smaller aliquots of liquids and distributing the latter individually and in parallel to different microchannel structure of the same microfluidic device (unit C), d) quick penetration into a microchannel structure of an aliquot of a liquid dispensed to an inlet port of a microchannel structures (unit D), and e) volume definition integrated within a microchannel structure (unit E). There may in addition also be other structural units and/or microfluidic functionalities included.
II. Related Art
Microfluidic structures have been considered promising for assays, chemical synthesis etc. which are to be performed with a high degree of parallelity. A generally expressed desire has been to run the complete sequence of steps of test protocols, including sample treatment within microfluidic devices. This has lead to a desire to dense-pack microchannel structures on planar substrates (chips) and to integrate valve functions, separation functions, means for moving liquids etc. within microfluidic devices. In the macroscopic world these kinds of functionalities can easily be integrated into various kinds of liquid transportation systems, but in the microscopic world it has become expensive, unreliable etc. to miniaturize the macroscopic designs. The situation becomes still worse when moving from μl- to nl-aliquots or from microchannel dimensions of above 100 μm down to those less than 100 μm. One of the main reasons for this is that the surface forces of liquids are more influential on liquid behavior when going down in volume from the μl-volumes to the nl volumes and smaller, for instance when going below 5 μl. A typically example is that wicking/imbibing will promote quick liquid transport from a nl-vessel making it difficult to retain a specified liquid volume in such a vessel.
I. Centrifugal Force for Moving Liquids in Microfluidic Devices
The use of centrifugal force for moving liquids within microfluidic systems has been described for instance by Abaxis Inc (WO 9533986, WO 9506870, U.S. Pat. No. 5,472,603); Molecular devices (U.S. Pat. No. 5,160,702); Gamera Biosciences/Tecan (WO 9721090, WO 9807019, WO 9853311), WO 01877486, WO 0187487; Gyros AB/Amersham Pharmacia Biotech (WO 9955827, WO 9958245, WO 0025921, WO 0040750, WO 0056808, WO 0062042, WO 0102737, WO 0146465, WO 0147637, WO 0147638, WO 0154810, WO 0241997, WO 0241998, WO 2002074438, WO 2002075312, WO 200275775, WO 2002075776). See also presentations made by Gyros AB at various scientific meetings: (1) High-through put screening SNP scoring in microfabricated device. Nigel Tooke (September 1999); (2) Microfluidics in a rotating CD (Ekstrand et al) MicroTAS 2000, Enschede, The Netherlands, May 14-18, 2000. (3) (a) SNP scoring in a disposable microfabricated CD device (Eckersten et al) and (b) SNP scoring in a disposable microfabricated CD device combined with solid phase Pyrosequencing™ (Tooke et al) Human Genome Meeting, HGM 2000, Vancouver, Canada, Apr. 9-12, 2000, (4) Integrated sample preparation and MALDI MS on a microfluidic compact disc (CD with improved sensitivity (Magnus Gustavsson et al) ASMS 2001 (spring 2001).
II. Unit A: Retaining Microcavity for nl-Aliquots
The proprietor of the present invention has during the last year developed microfluidic systems comprising structural units comprising microcavities intended for nl-volumes of liquids. See for instance WO 9955827, WO 9958245; WO 0040750, WO 0146465, WO 0147638, WO 0241997, and WO 0241997 and scientific presentations made by Gyros AB (see above). Hydrophobic surface breaks for preventing undesired creeping of liquid around corners or as valves have in particular been emphasized in WO 9958245. See also WO 2002074438, WO 2002075312, WO 2002075775 and WO 2002075776.
III. Unit B: Mixing Unit
Units for mixing aliquots within microfluidic devices have previously been described. These units have been based on (a) mechanical mixers in mixing microcavities or microconduits including creation of turbulence by fixed streric hinders (e.g., WO 9721090 and U.S. Pat. No. 4,279,862 (Bretaudiere et al)); (b) creation of turbulent flow in a microcavity by two incoming liquid flows (e.g., WO 9853311); (c) creation of a laminar flow in the inlet end of a mixing microconduit and achieving mixing by diffusion during the transport through the microconduit (e.g., U.S. Pat. No. 5,637,469, (Wilding & Kricka); (d) mixing by pumping layered aliquots back and forth in a mixing microcavity or microconduit. This can be accomplished by applying pulsed centrifugal force by spin pulses that drive the liquid in one direction and a higher spin pulse and in the reverse direction at a lower spin pulse utilizing energy built up in the system during a high pulse for driving the liquid in the reverse direction during a lower spin pulses. This can be accomplished by utilizing enclosed air ballast chambers and/or hydrophobic/hydrophilic as outlined in WO 0187487. The principle of back and forth transport is also described in WO 2002074438 (unit 5) and WO 9958245.
IV. Unit C: Distribution Manifold
According to the inventors knowledge publications related to this topic are rare. U.S. Pat. No. 6,117,396 (Orchid) gives a non-centrifugal gravity based microfluidic device in which a common reagent channel is used both as an overflow channel and as a reagent fill channel. A plurality of parallel volume metering capillaries is connected at different positions to the reagent fill channel from below. A centrifugally based distribution manifold for microfluidic systems has been given in WO 9958245 and WO 0187486. This latter variant is based on an annular distribution microconduit and comprises at least one waste/overflow microconduit per aliquot to be dispensed.
Microfluidic devices with a microchannel structures that comprises a part that bents towards a lower level (downward bent) and/or a part that bents towards a higher level (upward bent) have been described previously. Downward and upward bents have been linked to each other in short series. Bent structures for centrifugal based system have been used for metering liquids, process chambers etc.
Downward bents have been combined with centrifugal force and used for retaining liquid (valve function) that is to be subjected to distinct process steps in the bent, e.g., chemical or biochemical reactions, affinity reactions, measurement operations, volume metering etc. By including an outlet microconduit with a valve function, for instance a passive valve, in the lower part of the bent, processed aliquots can been transported further downstream in the structure in a controlled manner.
Further details about previously known bent structure are given in: WO 9958245; WO 0147638; WO 0146465; WO 0040750; WO 2002074438, WO 2002075312, WO 2002075775 and WO 2002075776; WO 0241997 and WO 0241998. Bent structures have also been indicated in scientific presentations made by Gyros AB and given elsewhere in this specification.
V. Unit D: Inlet Port
Imbibing has been utilized to promote liquid penetration into microchannel structures by including edge/corner structures associated with inlet ports. See U.S. Pat. No. 4,233,029 (Eastman Kodak) and U.S. Pat. No. 4,254,083 (Eastman Kodak).
VI. Unit E: Integrated Volume-Defining Unit
Integrated volume defining units in microfluidic systems are previously known. U.S. Pat. No. 6,117,396 (Orchid), for instance, gives a non-centrifugal gravity based system in which a common reagent channel may act as an overflow/filling channel along which there is spaced a plurality of volume metering capillaries for μl-volumes. Integrated units for metering volumes in centrifugal based system by the use of an overflow channel have been described in WO 9853311, WO 0146465 and WO 0040750.
The present invention is the first to provide novel fluidic functionalities that are used when transporting and processing nl-volumes of liquids in microchannel systems, which are defined herein.